texts: How would the temperature on earth be if the sun was slightly more or less powerful?

texts:
The temperature on earth is around 14C celsius.
It is around 1370 W/m^2 from our sun. The earth has an albedo of around 0.3
On Tatooine (from Star Wars) i have been able to calculate it goes from 1066 W/m^2 to 2100 W/m^2 (depending if the stars eclipse each other or not). Tatooine is a desert planet with a albedo of around 0.4. How can i make a simplified function to calculate what the temperature ranges from on Tatooine?
I did read on effective temperature on wikipedia, but that is higher than the level in my physics class so i didnt understand.
In the movies they say the temperatures get quite cold at night and warm during the day, so i would expect it to go something like -10C to 40C.
We can just assume the atmosphere is the same as on earth since it is breathable for humans.
Considering as the albedo increases, the temperature should decrease with an increasing albedo.
Therefore my first attempt was
T=k(1-a)*P, where T is temp, k is a constant, a is albedo and P is w/m^2
Since the atmosphere is the same, k should be the same?
Therefore
287=k(1-0.3)*1370, solving for k gives us
k=0.3
therefore temperature on Tatooine should follow the function
f(x)=T=0.3*(1-0.4)*x-273 (to get it measured in celsius)
Where 1066<x<2100.
f(1066)=-81 and f(2100)=99
the temperature are not this extreme doe, so this wont work.
I am aware this is not an accurate science, but im taking my first physics course in high school now, so I dont understand the "proper" way of doing this. Is it completely incorrect to assume temperature is proportional to (1-a) and how much power the sun gives us, when its the same atmosphere (ish)?
If anyone wants how i found out the power the twin suns gives Tatooine i can share it here.


texts:
I am looking for a particular set of information to essentially make a star map for a game.

What I need:
All stars within 11,462 light years of Earth.
Their stellar classification.
If they have any planets around them (hypothetical or otherwise)
Their position using an x, y, z coordinate relative to earth or galaxy center (I don't really get declination, etc)

I need the extrapolated position/distance data, not the catalogs themselves.

The best one I can find is HYG, HabCat, and HYGHag is limited to to like 120,000 of 1,2 billion estimated stars... Are there any better?


texts:
The Space Exploration SE question When our Moon is hiding Mars, is it possible to create a radio communication between Earth and Mars? links to this short article in the popular press Mars is hiding behind the Moon this morning with the sub-headline

It’s a twice-a-year occultation; like the eclipse, but it’s Mars, and there’s no shadow

As answer(s) to the question mention, the Moon is smaller than Earth so an occultation would not be visible everywhere on Earth, so let's just consider it an occultation if it happens anywhere on Earth.
Question: Does a lunar occultation of Mars happen twice a year? Is the Moon's diameter big enough and it's orbit's inclination with respect to the ecliptic small enough that it can pass between Mars and some place on Earth twice a year?


texts: How do you calculate length of day in a multiple-star system?

texts:
How can you calculate the length of day for a planet (given a particular latitude and longitude on that planet) orbiting multiple stars?

What about a planet that is orbiting one star, but that star has another star orbiting it?


texts: How can I get the fluxes of fetch_imaging_sample? - astroML

texts:
I'm working with astroML in Python and I need to get the fluxes from the magnitudes in r band of fetch_imaging_sample().

from astroML.datasets import fetch_imaging_sample
data = fetch_imaging_sample()
mag = data['rRaw'] # these are the magnitudes in r band
err = data['rErr'] # these are the errors in r band

How can I get the fluxes with their errors?

Explain of fetch_imaging_sample: http://www.astroml.org/modules/generated/astroML.datasets.fetch_imaging_sample.html


texts: What size objects can be created from collision of two asteroids?

texts:
Does collision of two asteroids necessarily create only very small objects? (and how big is it "very small"?)

I am especially interested about collision of two asteroids with similar orbits (and thus relatively small difference of the speed vectors in the moment of collision).

Can such a collision create big (say 1km, or maybe 100m) objects?

Is it in this case likely that a created object would have something like a comet tail consisting of dust and small objects (probably gravitionally attracted to the resulting asteroid remnant)?


texts: Where are Moon's Apogee and Perigee? Do they rotate too?

texts:
Where are Moon's Apogee and Perigee? Which one is inside, towards the Sun, between Sun and earth?

Do they rotate too just like the north, south node?

Does Moon always need to be on Apogee/Perigee for it to be Full/New Moon?


texts: Has Hawking Radiation Ever Been Observed?

texts: I know Hawking Radiation has firm theoretical footing, but has a signal ever actually been observed? What observational research is being done to attempt to see this effect? Is it simply too tall an order (i.e. - too far away, too weak of a signal, etc..)?


texts: Transformation from Geocentric Coordinates into Equatorial Coordinates?

texts:
I have the moon's position in equatorial coordinates (RA and Dec) and now I want to calculate same moon's position in terms of earth centered coordinates i.e. Geocentric (latitude & longitude). My main goal is to establish a c++-code that gives me this transformation from RA,Dec to Lat,Lon and vice versa.

EDIT: More precisely, I have moon’s position in equatorial geocentric coordinates with following details:

Origin: Center of Earth
Lat   : Declination With fundamental Plane: Celestial Equator
Lon   : R.A.        With Primary direction: Vernal Equinox

And I am able to obtain the moon’s position corresponding to a specific Modified Julian Date (MJD). I am also able to calculate moon’s position in xyz-coordinates by following calculations

$X= EarthMoon*sin(PI/2.-dec_moon*deg2rad)*cos(ra_moon*deg2rad);$
$Y= EarthMoon*sin(PI/2.-dec_moon*deg2rad)*sin(ra_moon*deg2rad);$
$Z= EarthMoon*cos(PI/2.-dec_moon*deg2rad);$

where EarthMoon is the distance between Earth and Moon. Further, I am converting them into Horizon Coordinates (topocentric) w.r.t to an observer at a specific location by using my subroutine and this part done.

Further, I am initiating my simulated CR-particles from observer site. E.g. vCR[3]= {R,lat,lon}

vCR[3]={Rearth+2300, 31.30, 55.74} //Geocentric CS (earth-based)

And converting them into Geocentric Cartesian coordinates(x,y,z). Finally, I have

vM[3]={X,Y,Z}; in Equatorial geocentric coordinate system
vCR[3]={x,y,z}; in Geocentric Coordinate System i.e. Earth based

That is my particular question in which I want to make vM[moon position] and vCR[CR position] to lie in same coordinates to get my final result. i.e. transformation from Geocentric (R,lat,lon) into Equatorial Geocentric (h,R.A,Dec).
Note: For vCR[3]: zero-longitude is the Prime Meridian, Greenwich whereas for vM[3] it’s vernal equinox in celestial sphere there is the difference.


texts:
It appears that the face of the moon "rotates" clockwise from the time the moon rises to the time it sets. Tycho's crater seems more to the left and the "Rabbits head" looks like it's facing down more.

I know that is not actually the case but I am having trouble visualizing why this appears so. Can anyone explain?


texts: Understanding expected TESS data structure

texts:
I'm interested in trying to use the data that will be returned by TESS to apply some machine learning/computer sciences concepts. I'm not sure yet what I want to try to do with it (though I have some ideas - see end comments). This because I don't really understand the data structure it will be using.

So essentially I would like to first some help to get a high-level view of how the TESS data is structured. Then a bit of guidance as to how I could visualize it/get started with some basic example

Additional info/what I know at this point

I've checked out the MAST page. It details what type of FITS documents will be returned.

I have downloaded samples of some of these data products and I see they all come in FITS format. On Ubuntu, you can open that in Aladin. However Aladin in itself is a fairly involved piece of software. Do I need Aladin for this, or are there simple alternatives to just view the data quickly to help get a feel for what it means? In other words what kind of navigator do you use for FITS files?

I'm pretty new to astronomy - I'm coming at this rather from a computer science perspective. Some basic suggestions as to what kind of observation an amateur astronomer might want to look at would be welcomed if you have some.

The data linked above (MAST page) are simulated data (real data will only be available in a couple months). This is fine - mostly interested in being functional with the data when they arrive.

Data analysis ideas:

Using kmeans or similar to try to extract  what are some of the "typical" transit light curves

Generating those transit light curves from the raw data, say from a target pixel


texts: According to my calculations Jupiter's moons do not follow Kepler's 3rd law - Why is that?

texts:
I'm asked to collect data on the orbital properties of the four Galilean satellites of Jupiter and show that they obey the same scaling as in Kepler's 3rd law.

My approach for moon Io:

Online, I found that the distance from Io to Jupiter is 422,000km ~= 0.00282089577 AU
which is

$2.82\times10^{-3} AU$

Io's orbit around Jupiter is 1.77 Earth days; 1.77/365 ~= $ 4.85\times10^{-3}\, \mathrm{Earth\ years}$

By Kepler's 3rd law, $P^2(\mathrm{Earth\ years}) = a(AU)^3$

Thus

$(4.85\times10^{-3})^2 = (2.82\times10^{-3})^3$ which is obviously not true even just by looking at the powers of 10 after distributing the exponent on each side.


texts: We should be seeing more than 59% of the Moon

texts:
It is said that we see about 59% part of the Moon due to libration. However we must be seeing more than that. My logic is as below.
Since the Moon's orbit is inclined to the plane of Sun-Earth by 5 1/2 degree, when Moon is at farthest and lowest point below the plane, we can see beyond the North Pole of Moon from the Earth's North pole and similarly when the Moon is above the Sun-Earth plane we can see much beyond South pole of the Moon from Earth's South Pole.
Thus we must be seeing more than 59% due to inclined orbit of Moon.


texts: What would happen to a polished marble statue left in space for a million years?

texts: Consider it doesn't collide with any other objects. Would it be preserved perfectly in the vacuum or would its surface be damaged by anything like UV rays, radiation, gas, space dust, etc?


texts: Are trojans in L5 more likely than in L4?

texts: Mars has much more trojans in L5. Does it reflect a common pattern?


texts: Why are most discovered exoplanets heavier than Earth?

texts:
Looking at all discovered exoplanets (4393 exoplanets), I found than only 17 of them (less than one percent!) have masses less or equal to Earth's mass. Why so?

Is it because it is very difficult to discover an exoplanet of a low mass?
Is it because of the mass distribution, so that Earth-mass planets are very rare?
Is it because of the some other physical limitations?

According to Wikipedia:

The minimum mass/size required for an extrasolar object to be considered a planet should be the same as that used in our Solar System.

From another article:

A dwarf planet, by definition, is not massive enough to have gravitationally cleared its neighbouring region of planetesimals: it is not known quite how large a planet must be before it can effectively clear its neighbourhood, but one tenth of the Earth's mass is certainly sufficient.

So, where are all these planets that are lighter than Earth? Personally, I suspect that it's very difficult to detect these (relatively) low-mass planets. If so, are there any theoretical limitations that prevent formation of low-mass planets?
Note 1: most of the planets (around 70%) from the mentioned catalog do not have masses (i.e. there's no estimate for the mass of a planet). Most of the rest have $\sin i$ mass estimates. That might be one of the reasons.


texts: Massive degraded impact crater on Mercury - chemical evidence?

texts:
The planet Mercury has a myriad of impact features - this has been known for some time. However, observe in the following images, a relatively large 'High-Mg region' detected on the planet (below):

Image source: Messenger website

From the group's press conference website, they state that:

  The unusual composition of the high-Mg region and the relatively thin crust in this region suggest that it may be the remains of an ancient and highly degraded impact basin.

How is the 'unusual composition' of this region suggestive of being the remains of an ancient, highly degraded, impact basin?


texts: Universe’s Glow Shows There Are Fewer/More Galaxies Than We Thought, Say Scientists

texts:
There are several articles like this:
Universe’s Glow Shows There Are Fewer Galaxies Than We Thought, Say Scientists

NASA’s New Horizons spacecraft beyond Pluto has made a groundbreaking measurement of the Universe’s background glow—with astonishing results. It turns out that there are many fewer galaxies out there than previously thought.

But then they seem to say the opposite:

“The Universe is dark, but not as dark as we thought,” said Lauer. Having measured the Universe’s glow, Lauer and his colleagues subtracted known sources such as the stars in the Milky Way and reflections from interstellar dust only to find that some light remained unaccounted for.
So what’s the source? Options include:
...
There are many more faint, distant galaxies than theories suggest.

Is it more or fewer? Or am I misunderstanding something?


texts: What's the difference of the oldest light and newest light?

texts: Excuse an amateur question, as inspired by this question: "How old is the oldest light visible from Earth?", how to determine the age of light? Does light get old? Does light have characteristic therefore we know this light "A" is different from that light "B" therefore we can track how it going over time? Like tagging animals to observe their activities? How to differentiate one light from the other?


texts: Is there a useful measure of how "life-dominated" a planet is?

texts:
If life exists on Mars or Venus, then in contrast to life on Earth, it must be "just scraping by". I can imagine a few ways to quantify this:

Life on Mars or Venus is hard to detect -- any biosignatures are extremely faint (life doesn't seem to appreciably affect the chemical composition of these planets).

Life on Mars or Venus doesn't seem to play a major role in the important geochemical cycles on those planets.

Life on Mars or Venus doesn't seem to "use" much of the available energy in the environment, or to affect flow of energy from the sun to the planet and then back out into space.

By contrast, life on Earth has had dramatic effects on the chemical composition of the atmosphere and surface of the planet, plays a major role in many of the geochemical cycles on the planet, and an appreciable fraction of incident sunlight is siphoned into the food web by photosynthesizers before being radiated back into space.
One could imagine planets even more life-dominated than Earth -- harnessing more of the sun's energy, controlling cycles like plate tectonics, ocean currents, and wind patterns, affecting the magnetic field or orbital parameters of the planet, controlling the cratering rate or chemical composition by diverting nearby asteroids or asteroid mining, ...
But in any event, it's not clear to me whether there is a single good quantitative measure which might reflect many of these sorts of ways that life could affect its planet, such that Mars and Venus (if they have life) score low, Earth scores higher, and a hypothetical planet (or future Earth) might score higher still.
Question: Is there such a measure?
P.S. I could probably use some help choosing appropriate tags.


texts:
Newly born stars often have bilateral jets of gas ejected from them at high speeds (hundreds of km per seconds), often ending in Herbig-Haro objects. As I understand it those jets would have something to do with the star's magnetic field.

How does this work? How can a magnetic field cause the high-energy ejection of matter?


texts:
I know the exact time a radio telescope detected a transient event. I also know the exact location of the telescope, and the galactic coordinates (galactic longitude, latitude) and right ascension and declination of the beam pointing center.
I conjecture that the event was also observed by another receiver at another location. How can I correct for the time difference between the two locations (i.e. the event reached one observer earlier than the other due to that they are in different locations)? Currently, I’m taking the dot product of a vector between the known observer and the source, and a vector between the known observer and the potential observer, and dividing that by the speed of light. To obtain the vector between the observers, I calculate their ‘n-vectors’ ( https://www.movable-type.co.uk/scripts/latlong-vectors.html  ) and take the difference. However, I’m getting nonsensical delay values.


texts: Has the Lyman-alpha forest ever been used to test Arp's theory?

texts: Has the Lyman-alpha forest ever been used to test Halton Arp's theory that quasars are not cosmological but instead are ejected from relatively near-by galaxies?  If Arp was right, then the spectra of the quasar and the 'parent galaxy' should both show the same Lyman-alpha forest; if it only appears in the quasar spectra, then the quasar must be much further away.


texts: Are there bodies in the Universe that are not spinning?

texts: Do we know of a celestial body which doesn't spin at all on its own axis? If not, why is it so?


texts: My research has told me astronomers have labeled the galaxy arm that our system is located the Orion Arm but I have yet to find out if that also applies to Zeta Reticuli or not (not asking about aliens or anything, just trying to get my locations straight).


texts: How to use an app to help find deep sky objects in general, either attached to a telescope as a finder scope or held on hand?

texts:
A friend with a young child asked me for a beginner scope recommendation of less than $300 to see the planets as well as some brighter deep sky objects in a relatively dark suburban location. My first inclination is to recommend the Starblast 4.5 using a more novice-friendly Orion 7-21mm zoom eyepiece, but I think a major hurdle for complete beginners like her is not knowing how to star hop to find deep sky objects, and with a child around, patience is extremely limited.
With the current technologies on the night sky phone apps, I thought it might be useful and much cheaper than buying GOTO scopes to attach the phone to the manual telescope, such as a Starblast, to use as a secondary finder. I found YouTube videos about apps:

             (Sky Safari Pro) or like this

             (advanced app), but I don't know if amateur astronomers actually use the phone as secondary finders now. (Since I was last active with an astronomy club over 15 years ago, before any night sky phone apps became popular!) I searched online, but most web pages are not recent. So I am writing here. Do people now attach a finder-app loaded phones/iPads to telescope bodies as a secondary finder? If so, what apps do they use and does it work well (does it need frequent realignment)? I'm thinking of using a bunch of masking tape to attach the phone to the Starblast, or are there piggyback mounts I can buy for the Starblast?

If the above is not an option, I did find the Sky Safari Pro tutorial,

            , where you hold the phone/pad with this app to help guide the manual telescopes to find the objects, where the biggest advantage in star hopping is that the app can flip the stars as they are shown in the upside-down view through a Newtonian scope like Starblast. For people who have tried the Sky Safari Pro tool holding the phone/pad on their hands to help with their manual scopes locate objects, is it easy to use and helpful in the field?
Are there other recommended apps helpful in finding deep sky objects?


texts: Aren't there more naked-eye-visible stars in the Milky Way plane?

texts:
Most stars which are visible to the naked eye are within 1,000 light years. The Sun is inside the Orion arm which has a diameter of about 3,500 light years. Thus, all stars (with very few exceptions) we can see unaided are inside the Orion arm and should be equally distributed in all directions. The structure of the galaxy is too large to affect the distribution of visible stars.

Still, we do see the Milky Way disk. What is it we see? The dim light of stars we can't make out individually? Or star light reflected by gas clouds? And is the density of stars to the unaided eye really not higher in the plane of the Milky Way? (Since I'm living in a light polluted city I can't easily check it out myself)


texts:
I'm writing a sci-fi novel in which humans venture to the stars for the first time. Their "shake down" cruise takes them to Proxima Centauri. I'm trying to understand where Proxima Centauri is located relative to the sun rather than Earth, as that seems a more logical reference for navigation to nearby stars.

The location of Proxima Centauri in Earth's night sky is described with the Earth-relevant coordinates

  Right ascension   14h 39m 36.49400

  Declination –60° 50′ 02.3737

However, the Earth's orbit is inclined 7.155° to the Sun's equator and our axis is tilted at 23.4392811°.

Is there a reference indicating Proxima Centauri's sol-relative position, or can that position be calculated based on the above information?


texts:
I normally post on worldbuilding, but this question is merely about facts of a planets orbit and spin. I am trying to figure out how time periods work on Mercury to possibly make a worldbuilding guide for the planet. I recently heard on an educational video that the eccentricity of Mercuries orbit can cause the sun to temporarily become still on mercury, and then move in the opposite direction, then become still again, and move along it's normal course in the sky. The possible effects of this are that certain regions of mercury could experience a "season" where the son only goes partway through the sky before turning around and setting creating something of a cycle of "short days" and "long days". I imagine because of mercury's mathematically synchronized orbit, these short days can only be experience on small bands of the planet, I would imagine there is only one circular band going around the world along a line of longitude that is like this.
What I am trying to understand is how different parts of mercury experience the day and not simply the length of mercuries day in absolute terms. I am wondering how a hypothetical person that would be following the "evening" and "morning" sections of mercury would experience the backwards movement of the sun over the course of the mercurian year. I am wondering if this backwards movement of the sun causes one side of the planet to experience less daylight than the other side, but I will leave the practical effects of this on colonization for a worldbuilding SE.
Simply put: I am trying to understand how different regions of mercury experience the day/night cycle and the way the day/night cycle travels over the planet. This is ultimately a question of what mercuries natural time zones are and the length (and irregularity) of the day-night cycle on the different parts of the planet.


texts: Will the Magdalena Ridge Optical Interferometer be able to image extended objects like the surface of the Moon?

texts:
Inspired by several questions:

When will a moon landing site be visible via telescope?
Could the E.H.T. produce an image of the human artifacts on the moon?
Picture of equipment left on the Moon?
Were the Apollo lunar activities observed from Earth?

If one wanted to resolve 1 meter or smaller detail on the surface of the Moon from the surface of the Earth (about 2.6E-09 or 0.5 mas) at say 1 micron wavelength one would need a baseline of order 400 meters.

The longest current optical baselines are only 40 to 80 meters and the longest one currently under construction is the Magdalena Ridge Optical Interferometer which

  will have ten 1.4 m (55 in) telescopes located on three 340 m (1,120 ft) arms. Each arm will have nine stations where the telescopes can be positioned, and one telescope can be positioned at the center.

This is sufficient to have of the order of 1 meter resolution at the Moon's distance, but being optimized for star-like sources it's not clear if it will be able to image extended objects like the surface of the Moon.

Question: Will the Magdalena Ridge Optical Interferometer be able to image extended objects like the surface of the Moon, or is it designed only to separate a few star-like objects, e.g. binary stars or star + planetary systems?

note: If information on this specific observatory isn't available, it would be certainly informative to extrapolate from existing imaging work from long baseline optical interferometers. The Moon presents a big challenge since its surface brightness extends over quite a large solid angle, so pinholes at the focus of each telescope in the array would generate a lot of diffracted/scattered light, whereas imaging star-like objects against a dark field would be less susceptible.


texts: Best response to shut down the fake Moon landing conspiracy

texts:
This Question was closed for various reasons. For people looking for the answer to similar question, please see this link. I believe this is a solid answer to my question.

As the designated Space Cadet of my friends, I often have people come to me with questions regarding Outer Space. The most recent call came from a friend who was being aggressively told that the Moon landing was fake.

Now, we all know this is a conspiracy. In fact, conspiracy isn't actually the correct word per the definition. It's simply an incorrect claim. On top of this, we all have our return arguments to those who doubt the Moon landing. But I think anyone who has been in this argument has run into the typical conspiracy theorist issue:

As soon as you prove one claim to be false, they hit you with another that you need to fight against.

So, here is the question I ask all of us to think about:

What is a single fact/argument that completely debunks the claim that the Moon landing was faked?

(Emphasis on single fact/argument)

Disclaimer: I know that technically it isn't up to me to prove that the landing wasn't fake, but rather up to them to prove to me that it was fake. However, I still want to help people learn and be educated, so I would love some thoughtful answers to this question. Plus... I love a good argument (and I definitely love winning a good one too).


texts: Why are cirrus clouds more common on Mars?

texts:
Mars water  ice clouds are often associated with regional-
  to-global circulation and saturation conditions, as opposed to local convective overturning, and so typically exhibit cirrus rather than cumulus forms.

Source: The Atmosphere and Climate of Mars Edited by  Robert M. Haberle et al., 2017 - chapter 5 - subchapter 5.2

Why are cirrus clouds more common than cumulus clouds on mars?


texts: I am currently self teaching myself some basic astronomy. My book claims, if a constellation is observed for exactly 6 months during a year, then it lies on the celestial equator. I have failed to understand why this must be true. Shouldn't the visible duration depends on the position of the observer? For example, for an observer at equator, wouldn't all constellations (accept those at the polaris) be visible for exactly half a year? Also, is the constellation at the NCP always visible for people in the northern hemisphere? Thank you in advance!


texts: Why do black holes have jets and accretion disks?

texts:
If supermassive black holes possess the gravity required to prevent the escape of photons and other mass particles, why do jets and accretion disks form?

They seem to indicate that something is coming out of the black hole, while mathematics and physics seem to tell us that this is impossible.

It would seem that supermassive black holes only exert gravity towards themselves.


texts: Was there space before big bang? Or who knows there might be different heavenly bodies that we might not perceive?


texts: According to the big bang theory, the universe started from a small intial point and is essentially expanding. However, my question is that if the universe is expanding how is it possible for galactic collisons to occur? Are the galacies moving away from a relative position but not moving away from each other? If so, how do we know this?


texts: Best approximation for Sun's trajectory around galactic center?

texts:
What is the current best approximation for the path the Sun takes around the center of the Milky Way?

I have found some information on the approximate position of the Milky Way's center, the speed of the Sun's orbit, and the inclination/declination of the Sun's orbit. I have also seen models suggesting the Solar System oscillates up and down as it revolves around the galactic center.

I am wondering if there is any agreed upon approximation (a 3d plot of position vs time) that includes all of these factors.


texts: What would the night sky look like if the Milky Way were the only galaxy in the universe?

texts: I'm curious to know what the sky would look like without any other galaxies out there. How much do other galaxies factor into the stars we see? Does the Milky Way account for most of them? Would the night sky look normal? Or would it be very empty?


texts: What's the name of the measure of apparent (visible) size of a body? e.g. the Sun and the Moon appear to be roughly the same size, despite the Sun being vastly bigger - because the Moon is much closer. What's this apparent size called?


texts: Has life been discovered outside of Earth?

texts: I've just watched a movie that made me curious as to whether life has really been discovered on another world such as Europa??


texts: At the moment of total solar eclipse what are exact distances of Moon & Sun to the Earth

texts:
By total eclipse I mean the Moon and Sun are seen equal in size, neither of them is bigger.

For example, the Moon's average distance is 384000 km and the Sun's average distance is 149.5 million km. But when this distances occurs, are the Moon and Sun seen equal in size? (from Earth of course)


texts: How might Thales have predicted a solar eclipse?

texts: Thales of Miletus purportedly predicted a solar eclipse (most likely the solar eclipse of May 28, 585 BCE). The historicity of Thales' prediction can't be verified with any certainty given the sparsity of written records documenting the pre-Socratic era that have survived to present day. So, putting the historical question of whether or not he did aside, what plausible answers are there to the question of how he could/would have made such a prediction?


texts:
In this worldbuilding question, the moon is gone:

  an extra-solar gas giant passed close by Earth in which the Moon was
  knocked from orbit to become a planet in an independent orbit, as well
  as sending Mercury crashing into its parent star.

So by introducing a rogue planetoid, the orbit of both the Moon and Mercury needs to be affected, with at least the former surviving the encounter.

Is this possible? If so, what are the requirements (mass, velocity, proximity)?  Would it be possible for it to happen and affect the Earth minimally, so that it remains habital?


texts: The relation between the energy of star and heating effect

texts:
Because a star's temperature is an indication of the energy passing through each unit of its surface, it follows that for cool red and hot blue stars of identical luminosities, the cooler red star must be considerably smaller so that the energy escapes through a reduced surface area and has a far greater heating effect. Hence, knowledge of a star's colour and luminosity can reveal its size.

In particular, I can't understand the relation between energy and the heating effect. Of course, I searched for the word "the heating effect" in my own language. Also, I Googled in English.

In this context, what is the heating effect? Could you explain to me? If you give me any help, it will be very useful to me.


texts: Do the planets, asteroid belt, kuiper belt, and scattered disc lie on the same plane?

texts: If not, do any of the four groups in the title lie on the same plane as other members of the group? E.g. does the asteroid belt lie on the same plane as the planets do?


texts: Do tides occur on planets like Neptune, having water?

texts:
I mean, we experience tides here on earth because of combined effect of gravitational field of moon and sun. So I thought that tides could also occur on other planets.

Let us consider Neptune where the gas transits into a slushy ice and water layer. The water-ammonia ocean serves as the planet's mantle, and contains more than ten times the mass of Earth. Also it has 14  moons. What I was thinking was that more moons would mean more tidal effect would be seen even if distance from sun has increased.

But then I thought that the moons of Neptune would all have different orbits and different time periods of rotation. So this will definitely impact the extent of tides.

-To what extent will this affect tides?

And how will tides formed on Neptune be different than that             formed on earth? I mean, how will they vary in properties?


texts: Can the period of the planet transit across the sun be calculated in the same way the eclipse year is?

texts:
I read from Wikipedia$-$Eclipse cycle that the eclipse year, which is the period of Earth's hitting a certain node of its orbit around the sun, that is, the ecliptic, and the moon's orbit around Earth, can be calculated as the beat period of the synodic month and draconic month. The recent occurrence of planet transits across the sun lets me wonder if this principle can be applied to the case of a planet's transit across the sun as seen by an observer on another planet in an outer orbit.

When Venus transited across the sun on June 6, 2012, I read it takes place in pattern of the 8-year-interval pairs with each pair at the interval of 105.5 years and 121.5 years alternately, with one in each pair being when Venus crosses the ecliptic plane at its ascending node and the other being when Venus crosses the ecliptic plane at its descending node. This made me contemplate whether the period of the Venus transit across the sun when it crosses the ecliptic plane at its certain node can be calculated in the way the eclipse year is, that is, whether the following holds:

  The period of the Venus transit across the sun as it crosses the
  ecliptic plane at its certain node = The beat period of the period of Venus'
  being in inferior conjunction with the sun and the period of Venus'
  hitting that node.

Early this July I read from EarthSky an observer on Pluto may, through some optical aid, be able to see Earth transiting the sun on July 12, when Pluto was at opposition, which, together with the upcoming event, that on October 24, 2018 Pluto will cross the ecliptic plane at its descending node, is responsible for the Earth transit as seen from Pluto. Last time this kind of transit occurred on January 11, 1931 on account of both that Pluto was at opposition that day and that Pluto crossed the ecliptic plane at its ascending node on September 9, 1930. And next time this kind of transit will occur when Pluto is at opposition 161 years later, around when Pluto will cross the ecliptic plane at the same node it crossed in 1930. This makes me again contemplate whether what follows holds:

  The period of the Earth transit across the sun as seen from Pluto as
  Pluto crosses the ecliptic plane at its certain node = The beat period of the
  period of Pluto's being at opposition and the period of Earth's
  hitting that node.

I think the principal difference between the eclipse year and planet transit across the sun is that in the former case both the moon and the sun are in a closed orbit around Earth while in the latter case only the sun is in a closed orbit around the observer-sited planet (the transiting planet is in a tortuous path from the perspective of the observer). I don't know if this feature would affect the applicability of the beat-period principle. If the principle of beat period as it used to calculate the eclipse year can be applied to the above two examples, I think it should be able to be generally applied to calculate the period of any planet's transit across the sun as seen by an observer on an outer planet, right? That is, should what follows generally hold?

  The period of a planet's transit across the sun as seen from an outer
  planet as it crosses the outer planet's orbit plane at its certain node =
  The beat period of the period of the transiting planet's being in
  inferior conjunction with the sun from the outer planet's perspective
  and the period of the transiting planet’s hitting that node


texts: Are there stars with an average density greater than the central density?

texts: Are there likely to be stars for which the average density is greater than the density at the centre? Intuitively, I would say not, as density tends to decrease outwards, but ideally I would appreciate a clear mathematical justification for this.


texts:
I've always wondered how our planet Earth or any other large spheroid-shaped thing in our universe has gravity?

Does it have a small black hole on its core causing it to have gravitational force?

Take our planet as an example: what causes it to have gravity?


texts: Does a set moon sky equal a new moon sky?

texts:
I am planning some astrophotography. And comparing two times.

On one night I plan a midnight shoot when a waning crescent moon rises at 1am. This is 1 week ahead of the new moon.

The other night would be on a new moon.

Would the darkness of the sky be expected to be any different? I ask because a lot of articles I read about stargazing and astrophotography say the phases of the moon are important, but never mention the setting and rising of the moon as an important factor.


texts: What does the Sun's orbit within the Solar System look like?

texts:
Everything in the Solar System revolves around the "barycenter": the overall center of mass. This barycenter is not in the center of the Sun. Some articles and essays I've read go so far as to suggest that the position of the barycenter does not have a set of fixed coordinates within the System: it fluctuates.

Well. Since everything, including the Sun, revolves around this barycenter, the Sun must have its own orbit around it. What does it look like? How large is it? How elliptic?

(In my research, I have tried and failed to establish whether the barycenter is within the Sun or outside it. Either way, an orbit is an orbit).


texts:
Since I'm not a physicist, I want to know how that system works.
For instance, if there was a planet, very similar to the Earth, but with two moons, and the moons where in a horseshoe orbit, how does it work? Is it stable?
I need it explained in an easy way, and also how would the moons look like from the Earth?
Thanks!


texts: Why doesn't Titan have a carbon dioxide atmosphere?

texts: Earth's primitive atmosphere had large amounts of carbon dioxide, as did the ancient Martian atmosphere. Venus's current atmosphere is no exception either. So why does Titan have next to none of this compound? Is it due to its location with respect to the Sun?


texts: Can a meteor shower happen simultaneously all around the planet?

texts:
In the original book, the classic 1962 movie and the modern 2001 re-make for TV. The store "The day of the Triffits" depicts a meteor shower that happen all around the Earth at the same time, and leaves everyone who sees it blind the following days.

Given the nature of how the Earth rotates, moves around the Sun and a meteor field (required to create a shower of many meteorites). Is it really possible for such an event to happen everywhere at the same time?

This is kind of an important plot in the story, because if one side of the planet goes blind first they can warn the other.


texts: Are there any to-scale diagrams of the TRAPPIST-1 system

texts:
I was recently told that the planets in TRAPPIST-1 are close enough together that you can see them from each other, as visible, discernible planets "hanging in the sky". i.e. much like the moon.

I'm trying to understand the implications of the claim, and started by trying to find a to-scale diagram of some, or all, of the TRAPPIST-1 system. Showing the start, the planets, their sizes and orbits.

I couldn't find such a diagram. Does one exist?


texts: In theory, is there anywhere in the universe where velocity=0?

texts:
Earth is traveling at a certain velocity.  Earth orbits the Sun at velocity X.  The sun is orbiting the center of our galaxy at velocity Y.  The galaxy is orbiting (something?) at velocity Z. On and on...

In relation to zero, Earth has a velocity of X + Y + Z + (?).

Is it theoretically possible that there would be a point in space where nothing is moving and velocity is essentially 0?

If so, what would time look like at this point in space?


texts: How far can a planet with living beings get before we cannot see the living beings?

texts: Let there be a planet with Earth-like life. However, no trash or monuments or other visible structures, just organisms. How far can that planet be from Earth before our equipment just cannot observe the life anymore? Furthermore, let's say that our equipment is perfected and limited only by natural laws: how far can the planet be now?


texts: What features are different in old/young galaxies, what can be seen?

texts:
As you all know, the further the galaxy is from us, measured by redshift, the younger it is supposed to be, but what other features can be seen in those younger galaxies to confirm their age?
Hints: Some particular features of younger age stars, galaxy forms, what afaik changes at 10Gy .
I would be grateful for recommendations of some scientific articles with aggregation of all features and correlation with the "distance-age" measured by redshift.
Thanks a lot.


texts: How do isolated binary compact systems survive their formational supernovae?

texts:
In a broad sense I'm trying to understand how a binary black hole or neutron star systems can form from isolated binary massive star systems (i.e., other than from migration within rich BH/NS clusters), and especially, how these can form within the constraints that allow for observed merger rates. I was hoping that this question would answer me, but it doesn't, because I realised I've never seen an explanation of how a binary system could survive a SN of one of its stars in the first place.

As far as I understand, we think one route to observed BH/NS mergers is a binary system of massive stars. This gives a scenario of 2 massive stars in an isolated binary system, one of which undergoes core collapse and type 2 SN. The two stars must be quite close (or later perturbed) and not greatly "kicked" on formation of either compact object, otherwise they couldn't later merge in the observed time. They probably also have similar ages (formed in the same cloud).

But in this scenario

How does the second-to-collapse star, survive being ripped apart by a nearby SN at such short distance, and remain in a small enough orbit, which we know happens since we later observe the merger of two compact objects? How does it survive structurally and regain stability in a form capable of future SN, given the intense flood of neutrinos and other energy/particles, some of which can penetrate to its core? Or does the first SN directly trigger the second SN?
Even assuming the second star survives with enough mass and undisrupted structure for SN (or is triggered directly into SN), wouldn't the transferred momentum from the first SN ejecta "on its doorstep" be sufficient to simultaneously unbind the binary system, or the momentum transferred from the second SN be enough to eject the first NS/BH, so that the two resulting compact objects no longer form a binary system?


texts: If an object with mass were to somehow go the speed of light, would it destroy the whole universe?

texts:
Would an object with mass traveling the speed of light destroy the whole universe because it would have infinite energy / mass?  According to wikipedia and other sources, it takes infinite energy to go the speed of light, which should be impossible.  However, for the sake of the question, let's assume it were somehow achieved e.g. potentially as described here.

My premise behind it possibly destroying the whole universe is that an object with infinite energy should also have infinite mass ($e=mc^2$, and infinity / $c^2$ is still infinity).  Infinite mass should have infinite gravity, which may well destroy the entire universe (although, would this destruction travel at the speed of light, so it would "slowly" destroy the universe vs. instantly?).

One thought is that it could just form a black hole instead, but as I understand it, a black hole is an infinitely small (singularity) of infinite density, with a "net mass" equal to the net mass that it has ingested.


texts: I purchased a 10 pack of glasses for viewing the upcoming eclipse. They show to be ISO 12312-2:2015 certified. How can this be tested and verified?


texts: What did I see streaking across the sky last night?

texts:
I was enjoying a casual naked eye view of the summer sky last night around midnight in a new jersey beach town. The sky was pretty clear for around here.The Milkyway was just visible and there was no could cover or buildings higher than me so I saw from Cassiopeia to Sagittarius.

I was hoping for a meteor and I got one I have never seen before. I will try to describe it.

Appearance: .It appeared out of no where like any other meteor but it had no streak AT ALL. As it traveled it shimmered. It was blue colored and not particularly bright perhaps fuzzy. The shimmering was the best way I can describe it.

Trajectory: It began high in the sky slightly to the east around the "southern" part of the constellation Aquila. It traveled west. It was as fast as any other meteor but as I said had no tail. It lasted very long... say 4 or 5 seconds. It didn't have an arching trajectory like something lower. It traveled straight and as it disappeared, it seemed to travel off into vs down to the horizon.

I was so astonished that I practiced the speed it went with my finger after it finished. It moved from say Vega to Altair in less around a second.

It couldn't have been any kind of craft since it appeared and disappeared and traveled so quickly. I have seen 100's of meteors of many kinds but not any like this. What did i see?

I tried to be as detailed as possible. If I missed anything, I'll add it in the comments.

For the record, I am not a believer in visiting aliens or supernatural events. BUT you will laugh at this. Years ago,I had read about an Ozark superstition that if you say "Money" three times when a meteor appears, you will get rich. I liked that one and since I stargaze a lot, I figured I'd get the opportunity. Well I had my chance and then some but I was so astonished, I forgot to say it. Looks like I  will have to keep working for a living :)


texts: Does the Lagrange L1 point have a 'size'?

texts: Like in cubic kilometers, what is the size of L1 "area of influence"? being unstable I guess that size can vary?


texts: What effects does the motion of the Sun have on the perihelion precession of Mercury?

texts:
According to the wikipedia page, there are multiple effects contributing to the perihelion precession of Mercury.
Of course, according to this link and this link we know that the Sun is itself orbiting around a barycenter that sometimes crosses its own surface. Are there any calculations that tell us what effects this has on the perihelion precession of mercury?
Edit: I see now that you can do calculations in a barycentric reference frame or in a heliocentric reference frame. If one chooses to use the heliocentric frame (which is an accelerating frame), one would have to take into account "third body effects" on Mercury.
My question now comes down to the following: do we know whether or not these third body effects were taken into account in the calculation for the 532 arcsec/century value listed in the wiki link?


texts: Kepler's Law, focal points - Heliocentric or Barycentric?

texts:
It is known that all the mass in the Solar system moves around the Barycenter.
For the two focal points in Kepler's law; is the first focal point $F_1$ a Heliocenter? Or is it actually a Barycenter?
If the $F_1$ is a Heliocenter, then, can the same exact ellipse and eccentricity of orbit be maintained by adjusting the second focal point $F_2$ and taking Barycenter as $F_1$ instead of Heliocenter?


texts: Would Martian sunrise/sunset look the same at the Thaumasia Plateau as the rovers' photographs?

texts:
If observing the sunrise or sunset, with the naked eye, from the Thaumasia Plateau (app. 260°, -10°), 6 kilometers above Mars elevation zero,

would it have the same blue hue as the images of the sunrise/sunsets taken by the NASA rovers below elevation zero?

Would a higher elevation sunrise/sunset look any different because the atmosphere is less dense?


texts: Astrophysical black holes deviating from Kerr black holes?

texts:
Rotating black holes are formed due to the gravitational collapse of massive spinning objects. And, it is generally believed that Kerr black hole solutions are valid for the empty space outside of the astrophysical black holes.
My question: Are there some pieces of evidence (observational data) for astrophysical black holes indicating deviation from Kerr black hole solution?


texts: Compared to the effects an impact of a global killer would have on Earth, what if such an asteroid, with a diameter around 7 miles (11.2 km), impacted the red planet with its different atmosphere, size and gravity? Would any volcanoes erupt? And what effects would such impact have on the probes and rovers currently on Mars and on its exploration?


texts:
Not sure if this question belongs here, or on Physics. Would someone please describe the "anatomy" of a light cone and provide an intuitive example?

I have read the Wikipedia article (http://en.wikipedia.org/wiki/Light_cone) and I think I have a basic grasp of the concept. However, I still have questions: is a cone emitted every time there is a disturbance in the electromagnetic spectrum? Does every electron changing energy states emit a light cone? I understand the "future" light cone (I think). However, what of the "past" light cone? Is that what is observed when detecting redshifts?

Thank you for your answers/comments. They have helped my understanding of the light cone concept.


texts: Theoretical values of radius and mass of O9.5 II star

texts:
Where to find please theoretical values of radius and mass of O9.5 II star?

I mean something like in this article. However, there are only O I, O III and O V stars in this article.


texts:
This answer to the question What direct or indirect observations of dust can one make by eye or with binoculars? mentions Brian May's thesis and it's connection to Zodical Light:

Brian May (CBE):

In 2007, Brian May, lead guitarist with the band Queen, completed his thesis, A Survey of Radial Velocities in the Zodiacal Dust Cloud, thirty-six years after abandoning it to pursue a career in music. He was able to submit it only because of the minimal amount of research on the topic undertaken during the intervening years. May describes the subject as being one that became "trendy" again in the 2000s.

Brian May's Thesis: A survey of radial velocities in the zodiacal dust cloud
And for good measure, Brian May's announcement of IAU's naming of the asteroid 17473 Freddiemercury YouTube: https://youtu.be/o2vo6VR51eA

I believe that MgI stands for neutral, atomic magnesium, and since this is optical (not X-rays) this would have to be free atoms, or perhaps molecular, but not bound magnesium in compounds or metals.
Question: Why is there free magnesium in the ecliptic (if there is) and why would some be orbiting within the ecliptic plane but retrograde?

Here is the abstract of the thesis in full:

This thesis documents the building of a pressure-scanned Fabry-Perot Spectrometer, equipped with a photomultiplier and pulse-counting electronics, and its deployment at the Observatorio del Teide at Izaña in Tenerife, at an altitude of 7,700 feet (2567 m), for the purpose of recording high-resolution spectra of the Zodiacal Light. The aim was to achieve the first systematic mapping of the MgI absorption line in the Night Sky, as a function of position in heliocentric coordinates, covering especially the plane of the ecliptic, for a wide variety of elongations from the Sun. More than 250 scans of both morning and evening Zodiacal Light were obtained, in two observing periods – September-October 1971, and April 1972. The scans, as expected, showed profiles modified by components variously Doppler-shifted with respect to the unshifted shape seen in daylight. Unexpectedly, MgI emission was also discovered. These observations covered for the first time a span of elongations from 25º East, through 180º (the Gegenschein), to 27º West, and recorded average shifts of up to six tenths of an angstrom, corresponding to a maximum radial velocity relative to the Earth of about 40 km/s. The set of spectra obtained is in this thesis compared with predictions made from a number of different models of a dust cloud, assuming various distributions of dust density as a function of position and particle size, and differing assumptions about their speed and direction. The observations fit predominantly prograde models fairly well, but show a morning-evening asymmetry, different in the two observing periods. Models are investigated containing various components, including prograde and retrograde orbiting dust around the Sun, a drift of interstellar material though the Solar System, and light from distant emitting matter. The implications for possible asymmetries of the Zodiacal Cloud are discussed. Other researches on the Zodiacal Dust Cloud, before, during, and after my observations, are reviewed, including recent insights into its structure, orientation, and evolution, up to the present day, and my observations are evaluated in this context. Period of study, 1970-2007.

Source


texts: How difficult is adaptive optics computationally?

texts: What kind of computer do you need to do adaptive optics of big telescopes? Are we talking supercomputer clusters or can my desktop do it, or my smartphone? I suppose it depends on the size of the telescope and the wavelength that is targeted. I'm interested in both the kind of computers that are used and the actual number of FLOPs per second that is required.


texts: Was time different before the great inflation?

texts: In time different during the first second after Big Bang than it is now? Inflation had a dramatic effect on space, and spacetime is one thing. Was the properties of time affected too? Curved spacetime around black holes cause funny effects for outside observers, infalling objects appear to never reachthe event horizon. The very early universe was even denser. When we talk about the first second, are such effects accounted for?


texts: Is it still the case that the transit of Mercury can't be measured with sufficient accuracy to determine the Sun's distance?

texts:
The book Transits -- When planets cross the Sun, Maunder & Moore, page 44 states that

Legentil [was] one of the first to realise
that transits of Mercury could never be observed with
sufficient accuracy to make them really valuable in
measuring the length of the astronomical unit.

Is this still the case? With modern instrumentation, can the transit of Mercury still not be measured with enough precision to derive the distance to the Sun? If not, why not? Has Mercury never been used to determine the distance between the Earth and the Sun?


texts: Are there any known planets whose axis is oriented such that one pole always faces its star?

texts:
Earth rotates around the sun and around its axis (A North, South axis) giving us days, nights and seasons.

Are there any known planets that rotate with an axis pointing toward its sun so that one half of the planet is always facing it (the other half is always facing away from it)? Like Uranus, but not switching which side is facing the sun every 6 months.

(Would this even be theoretically possible?)


texts: Why do Black Holes in the middle of galaxies not suck up the whole galaxy?

texts:
As stated in several sources, it's supposed that in every galaxy there is a black hole in the middle.

My question is, why do these black holes in the middle of galaxies not suck up all the surrounding matter in the galaxy?


texts:
How to easily find out the periods when a planet gets into retrograde? for eg I want to find out all the periods, in last 5 thousand years, when mars goes into retrograde in Sidereal Scorpion?
Is there any website, or software, where I can find this using command or something like that as opposed to checking each year manually. Like approximately Mars wold have gone retro in Scorpion 250 times in the last 5000 years.


texts: What should I read next after Neil deGrasse Tysons "Astrophysics for people in a hurry"?

texts:
I really liked the clever way the author explained stuff in this book but I already understood most of it. Neil himself states in the book that if you are not in a hurry and want to know more about the topic the are plenty of bigger books you can look into. So my question is: what is sort of a next step after this book on this topic (astronomy, astrophysics)?
Thanks.


texts: Why is there a difference between the cosmic event horizon and the age of the universe?

texts:
According to wiki the cosmic event horizon is 5 Gpc but the age of the universe is about 13,7 billion years. Usually light from far galaxys needed at most 13,7 billion years to reach the earth so the event horizon should be the same. But in wiki the event horizon is 5*3,2billionly=16 billion ly. So is this difference just a matter of rounding or old data or is there something else what causes the differences?

https://en.wikipedia.org/wiki/Cosmological_horizon#Event_horizon


texts: How did "oddball" Valetudo, Jupiter's new prograde moon, end up in a wider orbit?

texts:
I just saw this question and that got me to this NASA page which led me to this scientific article.

“Our other discovery is a real oddball and has an orbit like no other known Jovian moon,” Sheppard explained. “It’s also likely Jupiter’s smallest known moon, being less than one kilometer in diameter”.
This new “oddball” moon is more distant and more inclined than the prograde group of moons and takes about one and a half years to orbit Jupiter.  So, unlike the closer-in prograde group of moons, this new oddball prograde moon has an orbit that crosses the outer retrograde moons.
As a result, head-on collisions are much more likely to occur between the “oddball” prograde and the retrograde moons, which are moving in opposite directions.
“This is an unstable situation,” said Sheppard. “Head-on collisions would quickly break apart and grind the objects down to dust.”

My question is, why are most of the moons that are further away from Jupiter retrograde orbits, while the ones extremely close to Jupiter are prograde orbits? What possible situations were required for Valetudo to end up where it is opposed to where the rest of the pro-grade moons are clustered? Pure chance / a series of unlikely events?


texts: What shape are black holes theorized to be?

texts: I have always been curious about what black holes (or their event horizons) would look like if we could directly observe them. I notice that they tend to be depicted as flat holes in space but it seems to me that they would be spheres. Is there a scientific consensus on this. Or is it a vague question?


texts: What happens with a globular cluster when it passes through a galactic disc?

texts: The orbits of globular clusters are crossing the disks of their galaxies, so they should sometimes pass through the disks. Are there any observed fluctuations in the clusters and in the disks themselves caused by such crossings?


texts: Asteroseismology; recordings of star vibrations duration and data availability?

texts:
A short video titled "Why Tess is recording the "sounds of stars" at the bottom of the page of the BBC News article Planet-hunter launches from Florida gives a short description of Asteroseismology by Astronomer Bill Chaplin of the University of Birmingham.

Presumably the sounds played here are some kind of photometric measurements of stars that have been played back a few orders of magnitude faster to make them audible.

I'd like to listen to more of them, or even download a .wav or similar file and have a look at the spectrum just for fun.

I managed to find this University of Birmingham website through searching, and it plays sound clips from four different stars when the cursor is hovered over each one (it takes a while to become responsive I assume due to downloading).

http://bison.ph.bham.ac.uk/~miglioa/M4PR/M4_beta0.html

Roughly how long is the observation time of the star necessary to produce these audio recordings of a few seconds in length?
Where can I find downloadable data; either these .wav sound clips or more traditional raw data files that I could analyze?


texts: How to see Saturn's rings through a pair of binoculars?

texts:
I have a pair of 15x70 binoculars. I would not say what manufacturer to avoid being the subject of 'hold'.

The current angular diameter is 15.5 arcseconds. I am wondering if that condition is enough to be able to see rings. My eyesight is fair.


texts: If two stars collide, what is the probability that they merge to form a single star?

texts:
After looking at What are the odds that the Sun hits another star? and answering it (crudely), now I'd like to ask the following:
What is the probability that if two stars collide, their cores merge to form one larger, more massive star?


texts: Up to 384 minor planets (including Pluto) qualify as planets?

texts:
In 2006, the International Astronomical Union redefined the definition of planet in order to exclude Pluto, Eris, and several other objects whose category was disputed. This new definition of a planet featured 3 criteria:

A planet must be massive enough to achieve hydrostatic equilibrum and
become ellipsoidal.
A planet must orbit a star or brown dwarf (with the exception of planemo).
A planet must be massive enough to clear any nearby objects.

Pluto and the other objects apparently failed to meet the 3rd criteria, as they had not cleared the nearby Kuiper belt objects, so they were reclassified under the term "dwarf planets".

But what if Pluto actually has met the third criteria? It's probably well-known by now that Pluto has 5 moons. The largest moon Charon is over half the size of  Pluto, and is frequently classed as a dwarf planet in its own right. The other 4 minor moons Nix, Styx, Hydra, and Kerberos, are much smaller then Charon, and are similar to the many asteroid-like moons found around gas planets.

The leading theory for how these smaller moons formed is that they are leftover debris from a collision between Pluto and another object, but it's just as likely that they were Kuiper belt objects that were captured by Pluto (just like the moons of Jupiter and Saturn). If they were captured, this means that Pluto has technically cleared 4 objects from its neighborhood, and so it meets the 3rd criteria.

The same logic can be applied to Eris, 2007 OR10, and the 400 other dwarf planets known to host moons. So should we have 392 planets, keep the current definition, or scrap or redefine the term "planet" entirely?


texts: Why would atmospheric absorption increase rather than decrease the antenna temperature in Penzias and Wilson's famous CMB observation?

texts:
The classic paper A MEASUREMENT OF EXCESS ANTENNA TEMPERATURE AT 4080 Mc/s begins:

Measurements of the effective zenith noise temperature of the 20-foot horn-reflector antenna (Crawford, Hogg, and Hunt 1961) at the Crawford Hill Laboratory, Holmdel, New Jersey, at 4080 Mc/s have yielded a value about 3.5° K higher than expected. This excess temperature is, within the limits of our observations, isotropic, unpolarized, and free from seasonal variations (July, 1964-April, 1965). A possible explanation for the observed excess noise temperature is the one given by Dicke, Peebles, Roll, and Wilkinson (1965) in a companion letter in this issue.
The total antenna temperature measured at the zenith is 6.7° K of which 2.3° K is due to atmospheric absorption. The calculated contribution due to ohmic losses in the antenna and back-lobe response is 0.9° K.

So, why would it increase? And, what is the significance of zenith in this sentence?


texts: Question about orbital direction on binary systems

texts:
I wonder if is possible to find a binary system in which one star is orbiting the center of mass in one direction and the latter orbiting in the opposite direction.
Would this transgress angular momentum conservation?


texts: Is it possible to observe Polaris and the Southern Cross from the equator during an equinox

texts: Is it possible for an observer at Earth's equator to simultaneously observe Polaris and the Southern Cross during an equinox?


texts: Astronomy/Astrophysics Project With C++/C/Python

texts: I am a Computer Science Engineering student, in the 1st year of college. I'm insanely interested in making a project regarding astronomy/astrophysics but I don't know where to begin from. I know C, C++, Python(not Scipy,Numpy or Astropy, but the basics. But I'm willing to learn those too). Can someone please give me some insights on what do make/do which would satisfy my aptitude in this field? My C++ and C knowledge are almost up to date, and I know basics of python, with all the data structures and basic libraries of Python. I'm interested in simulation stuff, but I don't exactly have relevant resources to learn those.


texts: What is the proper interpretation of a negative parallax?

texts: The Gaia data release 2 dataset has some parallaxes listed as negative. What is the proper interpretation of this? Should they be discarded as bad data? Use their absolute value to calculate the distance? Use them as-is and treat them as negative distances along the right ascension/declination vector?


texts: Do radio telescopes see other stars better at night?

texts:
As you know, we don’t see stars with the naked eye during the day because of the visible glare of our Sun.
As I understand our Sun emits radio frequency waves, too. Is there a radio ‘glare’ from the Sun such that radio telescopes can better focus on other stars during the night?


texts: Would a low albedo substance warm up Mars?

texts: If Mars were coated in a dark substance that absorbs sunlight (including infrared light), would this heat up Mars?  I am envisioning a fine dust that is dispersed into the atmosphere, but possibly settles on Mars's surface all around.  If we were able to change the albedo, possibly down to as low as 1%, would that make Mars habitable (temperature wise)?  If the albedo were changed all the way to 1%, could this even make Mars too hot?


texts:
I'm making a game in which I'd like to randomly generate star systems. Which is cool.

The trouble I'm having is working out exactly what limits I need to place on the generation. So far, the wikipedia hasn't been all that helpful. So some questions:

Rocky planets form within the frostline of a protostar. What's the radius of this line? What I'm sort of asking is that given a particular mass and density, what radius from that star is the line.
If the jovian planets form outside of this line; why have so many been found within this line in other star systems from our own? Is this only selection bias or is it more likely that our models are incorrect at this point?
How does the creation of the gas giants differ from the creation of the ice giants? Is it simply like a second "frost line" where there wasn't enough gaseous material to form a large jovian planet but plenty of ices to form ice giants? If so, how is the creation of the ice giants different to Dwarf planets?


texts:
Sometimes, you can see the Moon high in the night sky, which is illuminated from the side where Sun goes down but slightly from above. It is paradoxical when Sun hangs at the lower level above the horizon than the Moon. Sun can even go down behind the horizon, yet, the Moon is illuminated slightly from above.

The paradox is defined in Wikipedia and captured in this video

There is a video from "Vsauce"

http://youtu.be/Y2gTSjoEExc?t=280

which pretends to explain the phenomenon but fails, IMO. From his explanation I only get that light beam should deviate from the direct route to move along the orbital around the Earth, like if it is the Sun or Moon orbit seen from the Earth. But why? The nebular objects orbit because they have mass and gravitationally bound. Why should light beam travelling from Sun to the Moon bend the same way as if it orbits around the Earth? I do not get the explanations.

The popular explanation of the illusion does not hold the water

http://youtube/watch?v=Rsz2QNPprB8&lc=z134gjggimumexwgr04cdxbrnlattlwp5n40k


texts: Is it possible to get a glimpse of the Big Bang through gravitation waves?

texts: I read in an article announcing the detection of gravitational waves by LIGO that it will be possible to detect them from the Big Bang. Is this true?


texts:
I'm trying to build a 3D model of the Sun, Earth and Moon in in Javascript (using Three.JS, which relies on x,y,z coordinates for all objects) in order to simulate the Aug. 21 eclipse. I've successfully figured this out using the Kepler method that NASA describes, but would like to use the HORIZON ephemeris data for greater accuracy, given how sensitive the timing of an eclipse can be.

I've read up on celestial coordinates, but still can't quite figure out how to take the output of the HORIZON tool and convert RA, Dec, etc into 3D coordinates, the way the Kepler document outlines. Can anyone point me to an authoritative primer one how to get from celestial coordinates to geometric coordinates?

Coordinates based on AU are just fine -- I've already figured out how to scale that in the simulator.

Thank you!


texts: Is the pulsar map on the Pioneer/Voyager probes only meaningful for earthlings?

texts:
The Pioneer probes brought plaques (and later the Voyagers two golden discs) with a "pulsar map" imprinted on them. The purpose of the map is to make the position of the Sun clear for an alien intelligence, in the case they encounter the probes in the far future, by creating a frame of reference of known galactic pulsars with specified periods and their distance relations to the Sun.
Pulsars have nice properties for this goal; they can be detected from large distances (which gives a higher chance of some of them been known by both sides), their period is very specific, easily measured with clocks and can be unambiguosly matched to a specific pulsar (if known), and their period changes over time in a predictable manner (which allows for aliens to trace back the date of origin in which the map was made).
But I have a question. If pulsars are detected on Earth when their beams point towards us (the "lighthouse"/"becon" analogy) and there might be many pulsars that are not known by us due to us being ouside of the cone where the beam can point, then wouldn't the 14 pulsar used in the "pulsar map" only be evident for aliens in the immediate solar neighbourhood? Maybe a few pulsars can be observed by them in other parts of the galaxy but the 14 of them would cenrtainly not be the same set of prominent pulsars we know of, right?
What am I missing?


texts:
How to perform the conversion of (r,v) vector from ECEF to ECI (J2000) coordinate frame?

What I tried

I multiplied the matrix ([cosA -sinA 0] [sinA cosA 0] [0 0 1]) by the state vector, where A is Greenwitch mean sidereal time.

This equation shows that the Z axis doesn't change. However, I have the ephemeris of a real satellite in both coordinate frames, and there Z axis differs!
Where is the issue?


texts: Is there a way to know if there are/are not solar-system-like systems of objects without a star?

texts:
There's an extremely high amount of variation in All of Known Existence. We do see many many stars, with an extensive amount of evidence for planets orbiting around stars. However, is there are way to determine whether or not there's something like a 'dark solar system'? That's the only thing I can think of to call it.
This would be made out of a central body of mass, where the majority of material is located, with smaller planet-like objects in orbit around it, not unlike Pluto and its satellites.
Well, what about nearly-massive-enough-to-be-stellar objects? Why would there not be more of these - and the inevitable satellites involved in something of that mass - than there are solar systems?
I'm also assuming these would be made out of the same material that nearly everything else is, and I would expect them to be in abundance, so, could this explain the dark matter mystery? Assuming these dark systems are made out of the same - or mostly the same - material, wouldn't that also mean that spectral analysis wouldn't be able to determine if light from stars passed through the dark systems?
Intuition tells me someone has already debunked this, but I haven't been able to find an answer one way or the other. (yet)


texts: Why some stars appear to move differently when viewing device shakes

texts:
I was looking at Arcturus with a pair of binoculars, and noticed that when they vibrate due to my heartbeat, Arcturus seemed to move differently than the other dimmer stars.

I started playing with that visual effect and noticed that it happens both vertically and horizontally, and that I could even make it "overlap" with a nearby star.  It is like it either lags or is ahead of the others in terms of how it moves in the field of view as the binoculars do their slight shake.  Why is that?


texts: spider image in Samuel Oschin Schmidt Telescope DSS imagery

texts:
I was puzzled by image artifacts that appear in DSS-2 (blue) survey.
These images were taken by the Samuel Oschin Schmidt Telescope on photographic plates and later digitized. They are also available via the Stellarium DSS layer and can be found in the Stellarium web version too (e.g. search for TYC 1327-245-1 and zoom in).
In some images, one can even find a string of such artifacts, obviously resulting from the scanning process of the sky.
They look like images of the spider construction.
In example 1,4, a streak contains one such artifact; maybe a processing artifact?
In example 2, one will find a string of such artifacts (bottom right, outside the image; the image is limited to 60'x60', but there are several artifacts that run along a line, each about a degree apart, this is obviously related to the original sky scanning procedure). (Search for HD 44018 and you will find at least three of those on a line).
What is the optical effect here? Is this a form of stray light? Some form of internal reflection? It's a bit surprising seen the fact that these images were taken by professional users. The artifacts have a specific shape that probably reflects the original plate construction in the focus plane. Does anyone have a picture of that?
Some examples:

https://stdatu.stsci.edu/cgi-bin/dss_search?v=poss2ukstu_blue&r=6h19m24s&d=21h4m29s&e=J2000&h=60&w=60&f=gif&c=none&fov=NONE&v3=
https://stdatu.stsci.edu/cgi-bin/dss_search?v=poss2ukstu_blue&r=6h17m29s&d=20h48m26s&e=J2000&h=60&w=60&f=gif&c=none&fov=NONE&v3=
https://stdatu.stsci.edu/cgi-bin/dss_search?v=poss2ukstu_blue&r=6h18m10s&d=21h5m10s&e=J2000&h=8&w=8&f=gif&c=none&fov=NONE&v3=
(RED) https://stdatu.stsci.edu/cgi-bin/dss_search?v=poss2ukstu_red&r=13h18m39s&d=29h11m6s&e=J2000&h=60&w=60&f=gif&c=none&fov=NONE&v3=

for those interested, a few links to the web version of Stellarium where these artefacts appear (there is a small bug that prevents sharing URLs of stars that contain spaces)

https://stellarium-web.org/skysource/V537Lyr?fov=0.82770&date=2021-05-05T20:55:44Z&lat=51.04&lng=3.71&elev=0
https://stellarium-web.org/skysource/HD43509?fov=0.95220&date=2021-05-06T20:59:08Z&lat=51.04&lng=3.71&elev=0


texts: How to explain that Polaris is a circumpolar star in the sky of any North America city?

texts:
Circumpolar star definition: the stars that remain perpetually above horizon.

My explanation: Latitude affects the constellation we see and Polaris(the North star) has altitude of approximately 89.4 degree. For example, in Miami(25 degree latitude) the Polaris is 90-25=65 degree above horizon. This means that for any city above equator, people are able to see the Polaris.

My explanation is verbose and probably incorrect. Could someone provide a valid one?


texts: Are there any common characteristics of habitable planets?

texts:
Recently, over a thousand exoplanets were confirmed in one huge sweep which is a huge achievement and in the mix a dozen or so possibly habitable planets were confirmed as well. This made me wonder, Are there any common characteristics of (possibly) habitable planets? If so, what are they? Could scientists use these characteristics to locate them? Or are they using these characteristics already?

NOTE: Answers can be theoretical as well!


texts: Where's the Prime Meridian of celestial coordinates

texts:
...or what's the 'direction of vernal equinox'?

For both Ecliptic and Equatorial coordinate system, the Wikipedia article gives "Primary direction (0° longitude)" - "Vernal Equinox", linking to article on the event of the Equinox which never mentions any directions associated with it.

I guess the direction will be associated with the axis connecting the Sun and Earth during vernal equinox, but which direction of the line? Outward, with the meridian running opposite of the Sun, or inward, the meridian crossing the Sun at vernal equinox? Or maybe my guess is entirely wrong?

Generally, how would one go about converting celestial (ecliptic or equatorial) latitude to Earth latitude or vice versa - e.g. finding where on Earth an object of given celestial coordinates is in zenith at given time? The linked article has several formulas of converting between various celestial coordinate systems but either no conversion to Earth coordinates or I failed to understand some of the conversions.


texts:
What is superradiance? I came across this term recently (used widely to explain fast radio bursts). After googling a bit, what I understand is: When several atoms are confined in a very small area and one of the atoms emits a photon (spontaneously and randomly), it affects all other excited atoms in its neighborhood to release their excess energy at the same moment producing an intense flash of light. The small area confinement is such that the area is smaller than the wavelength of the photons.
In pulsars or FRBs, this is also called antenna emission/ spatial bunching. Researchers working on pulsars might be having a good knowledge of this phenomenon. The other type of coherent radio emission is synchrotron maser emission.
Can someone illustrate a bit more on this topic?


texts: Why is the Moon smooth near the equator and bumpy near the poles?

texts:
It looks as if it was polished by applying emery to its spinning equator.

My initial guess was that it was simply an illusion caused by light direction, but the terrain map shows the same phenomena.

Google Moon photo and terrain maps (source)

North pole mosaic assembled from photos by NASA's Lunar Reconnaissance Orbiter (source):

South pole shot by NASA's Clementine (source):


texts: Why didn't we have inflation when the theory of everything and GUTS broke symmetry?

texts: Inflation seems to have occurred when the symmetry breaking of the electroweak occurred.   But do we know of any reason why we did not have inflation when gravity separated from the other forces or the strong and electroweak separated?  Are all these other symmetry breakings associated with the Higgs field and a mexican hat energy distribution.  Sorry it is all a bit confusing.


texts: Will the Heat Death scenario ever occur or just the Big Freeze?

texts:
According to the Wikipedia page regarding the ultimate fate of the universe, heat death is a different scenario than the big freeze.

It states that in the big freeze, temperature will asymptotically approach absolute zero. However, the following section about heat death states that heat death may only occur if temperature reaches an eventual temperature minimum.

If temperature never truly reaches absolute zero (the temperature minimum), can heat death even occur in the first place?


texts: Are any supergiants translucent? Some have volumes thousands of times more than the Sun's while having maybe twenty times the mass of the Sun which makes them sound rather diffuse. If there was a very bright distant star behind the supergiant would we be able to see it?


texts: Collapse of a star below the mass of Chandrashekhar Limit

texts: How is Chandrashekhar Limit calculated? What happens to stars below the mass of the Chandrashekhar limit after they collapse?


texts: Why is the boundary of friends-of-friends (FOF) halo corresponding to iso-density contour?

texts:
The friends-of-friends algorithm (hereafter FOF) is commonly used to find halos in cosmological simulations. (For more information, please refer to here and here)
I found that some literature argues that the boundary of the FOF halo is corresponding to an iso-density surface. For example, Springel et al 2001 states

It
places any two particles with a separation less than some linking
length $b$ into the same group. In this way, particle groups are
formed that correspond to regions approximately enclosed by
isodensity contours with threshold value $\rho\propto1/b^3$.

More et al 2011 says

One could expect that for a given value of $b$, the FOF algorithm defines the boundary of a halo as corresponding to a certain isodensity surface, at least in the limit of large number of particles.

However, I can't understand the connection between the boundary of the FOF group of particles and iso-density contour. How to derive this connection in formula form? Does this connection need other hypotheses?


texts: Why didn't all the iron and heavier elements find their way to the center of the accretion disc in the early solar system?

texts: I guess that's pretty much it. I just heard that that a meteor fragment was found to be solid iron and it just seems inexplicable that it was floating around.


texts: Can the patterns in the CMB be detected by off-the-shelf antennas/sensors?

texts:
I recently wrote a paper (will attach soon if feasible) for an astronomy class that analyzed the usefulness of the Cosmic Microwave Background as a static reference for attitude determination. The main benefit of this over other attitude determination techniques is that the CMB has a constant pattern, even in intergalactic space. There is some variation over time, but it’s on the order of 1000+ years.

I was able to apply common computer vision algorithms to match randomly rotated rendered images of the CMB to their respective RA, Dec, Roll coordinates. These (completely unoptimized) algorithms tended to require a field of view of (Will find this in a moment) and a resolution of (Will find this in a moment) to be reasonably accurate.

One of my main assumptions is that it would be feasible to make a detector with sufficient resolution and signal-to-noise to be able to spot the CMB variation patterns within a few hours of observation. Is this true? What level of volume, specialization, and/or budget would be needed for this sensor: Cubesat? Smallsat? James Webb Space Telescope?


texts: How special is the Solar system compared with other planetary systems?

texts:
For example:

Most planets have circular orbit

What else?


texts: How fast would an observer have to travel in order to be able to study an entire star's life in one human lifetime?

texts: Humans live for about 80 years. A star, however, lives from 1 million to trillions of years, depending on its mass. If humans want to have a detailed study of the life of a $1 M_\odot$ star, how fast would they have to travel, and would it be viable?


texts: Are the darker blue/black areas in this picture what the atmosphere of Jupiter looks like without clouds?

texts:
This is a picture (mosaic?) of Jupiter's south pole taken by Juno (also shown below). It has gotten a lot of press, but I haven't seen anything, even in the scientific paper that accompanied its release, that answers the first question that came to mind when I saw it : is this a view into the inside of Jupiter? I seem to recall seeing IR images of Jupiter where the poles appear quite hot, which would be consistent with a "clear sky" providing a view of deeper, hotter layers. But how deep can see in this picture?

Edit: I am aware that this is a visible light image, and that visible light does not penetrate the cloud layer of Jupiter.

My question is whether part of the south pole of Jupiter is cloud-free, at least to a depth where atmospheric extinction limits our ability to see the clouds. This interpretation of the picture would assume that blue light penetrates deeper than red light into the atmosphere (clouds not included) of Jupiter, and that this is the reason that some of the clouds, presumed to be deeper, look blue, while some areas between them are essentially black.

Here is an example of a picture of Jupiter in IR, which shows the poles as being relatively hot. The troposphere of Jupiter (or any planet) is generally hotter the deeper you go, so the poles appearing hotter is consistent with less cloud cover at the poles. [

I'm aware that perhaps no-one, including the Juno team, knows the answer to my question. Some useful partial answers would include an estimate of the depth to which visible light could penetrate Jupiter's atmosphere in the absence of clouds, and whether blue light would penetrate deeper than red.


texts: Is the sun any brighter during a solar eclipse

texts:
I keep hearing that you can go blind during a solar eclipse.

Is the sun actually any brighter during a solar eclipse? This is how the media seems to frame it, and they suggest you need special glasses to view the eclipse.

But after some reading, it seems that the warning is about just not staring at the sun in general, and there is nothing special about the eclipse.

Is this the case?


texts: 22nd is shortest day in some places, but the 21st is shortest in other places. Can this be true?

texts:
The Winter Solstice in the Northern hemisphere in 2015 is December 22 at 04:49 UTC.  Where I'm located in Nova Scotia, Canada, that's December 22, 00:49 AST.  And so I would say the shortest day of the year is tomorrow, the 22nd.   But for my friends in Ontario, that's December 21, 23:49 EST.  And so, for them, the shortest day is today, the 21st.

Does this make sense?


texts: First Confirmed Visual Observation of Gravitational Lensing

texts:
Is it possible to identify the first direct observation of the gravitational lensing?

What object was lensed, and where did the energy detected fall on the electromagnetic spectrum?


texts: Is a wavy path possible for a shooting star?

texts:
I was camping recently (May 2014), and observed several shooting stars (very fast, short lived), a few satellites (very slow, long lived) and lots of aircraft (flashing lights) in the night sky.

All of the shooting stars appeared normal, as very fast streaks across the sky, which disappeared within a fraction of a second. All except one. One started fairly straight as normal, then took a completely unexpected wavy path (like releasing a balloon to fly around the room) towards the end of its flight. Then it winked out. What caused this?

Note, I was completely sober at the time, the sky was clear, and I believe this could not have been an aircraft or satellite because of its tremendous speed. Apart from this 'meteor', there was nothing else in the sky which could be interpreted as a firework.

Could this really have been a meteor, and what could have made it take this path? If not a meteor, what else could it have been?

(Note: I have tagged this 'UFO' because I'm not sure I can identify this object, not because I think it's an alien space craft).


texts: Please forgive the simplicity of my question.  I have only had basic science courses.  Common sense seems to indicate that planetary orbits should be very close to circular, any perturbations having been eliminated over the ages.  Could it be that the composition of the planet be influencing the pull of gravity to produce a different gravitational attraction due to its mass?  I mean that if a planet were composed all of one substance, would the planetary orbit be perfectly circular?  I think about earth having constantly shifting water and gasses and even solids that affect its own rotation.  Might these shifts also affect the orbit of the planet around the sun, or does the total mass of the earth and moon together determine the orbit?


texts: Moving object seen through telescope, what is it?

texts: I was using my telescope to look at a nebula, intell I seen a star like object that was moving at a moderate speed in a straight line and eventually dimmed out. My first thought that it was just a satellite but I could only see it through my telescope which makes me think that it was to small to be a satellite. I'm not sure.


texts: Calculating longitude from star culmination

texts:
Here is the problem: I need to calculate longitude of observing place. And I know time (in UTC+1) of star culmination (Sirius) and star altitude. I also know RA (right ascension) and Dec (declination) of the star and I also know RA of the Sun for that day. I already calculated latitude but I can't figure out how to calculate longitude.

Thank you.


texts: Error propagation methods for orbit parameters

texts:
Recently I've encountered an article in our local astronomical popularization magazine. It is about a well known task of Sgr A*-black hole's mass estimation. The article is written as a step by step guide for young researchers. For example, the orbital parameters of the S2 star should be found using a drawing on a sheet of paper.
That is why I believed there is no need for very precise calculations
for this task.
However, in addition to the $ x $, $ y $ coordinates of the S2 star, I was also given the corresponding uncertainty values $ \Delta x $, $ \Delta y $ (19  coordinate measurements for the time period from 1992 to 2003):
\begin{array}{|c|c|c|c|}
\hline
time    & x      &   \Delta x    & y      & \Delta y \\ \hline
1992.226 & 0.104 & 0.003 & -0.166 & 0.004 \\
1994.321 & 0.097  & 0.003 & -0.189 & 0.004 \\
...     & ..     & ..    & ..     &       \\
2003.353 & 0.077  & 0.002 & -0.030 & 0.002 \\
2003.454 & 0.081  & 0.002 & -0.036 & 0.002\\
\hline
\end{array}
Using direct least squares method for S2 orbital fitting by an ellipse I've found parameters
$a,\ b,\ c,\ d,\ e,\ f$ of the conic equation: $$ax^2+bxy+cy^2+ dx+ey+f=0$$  I've
also decided to simulate the error propagation in a Monte Carlo fashion to find
the uncertainty in the estimates of $a,\ b,\ c,\ d,\ e,\ f$. And I succeeded in that.
But, here is the question: is there any other appropriate,
"analytical" way (not a Monte Carlo method) to find the uncertainty in
the estimates of $a,\ b,\ c,\ d,\ e,\ f$ which may be used in usual astronomers' practice?


texts: What is the difference between wind, jet and outflow?

texts:
For jets, I found a pdf file here

  Jet: collimated beam of matter of high velocity

  sources: young stars, active galactic nuclei, $\mu$-quasars, gamma ray bursts, planetary nebulae, pulsars

  jet sources host accretion disks

How about winds and outflows? Can somebody make some clarifications for the three concepts， their correlation and difference?


texts: What is the great (platonic?) year? How could it be explained in laymen's terms?

texts:
How could a great year be explained in laymen's terms?
According to the definition in NASA's Aerospace Dictionary  it is a complete cycle of the equinoxes around the ecliptic that completes in 26000 years:

great year
(NASA SP-7, 1965)
The period of one complete cycle of the equinoxes around the ecliptic, about 25,800 years. Also called platonic year. See precession of the equinoxes.

Does this mean that every X years the March 21st and September 22nd will be in a different part of the zodiac and it will take 26000 years to make a full circle?


texts: What is the word for space that is in the solar system, but outside the heliopause?

texts:
Wikipedia says the definition of interplanetary space is

  the region dominated by the interplanetary medium, which extends out
  to the heliopause where the influence of the galactic environment
  starts to dominate over the magnetic field and particle flux from the
  Sun

While it defines the solar system as the region in which the sun is the primary gravitational influence

  The Sun's gravitational field is estimated to dominate the
  gravitational forces of surrounding stars out to about two light years
  (125,000 AU).

So, if the region outside the heliopause but inside the solar system isn't interplanetary space, then what is it?


texts: I'm looking for some reference listing spectral lines outside the visible spectrum.  (In particular, I'm looking for an element or compound that emits strongly in the 700-900nm range.)


texts: Does a magnet outside a black hole affect one inside it?

texts: If I had 2 really strong magnets, and I threw one into a black hole, while holding one outisde it at a safe distance, what would happen? Would the magnets affect each other in any way? Would one push/pull the other?


texts: Gravitational attraction of Sun on distant object

texts:
A hypothetical situation which will help me with a real-life problem.
Several stationary objects are placed at great distances from our Sun -- say 0.1 light year, 0.5 ly, 1.0 ly. Assuming no other influences;
What velocity would each have when it reached the Sun?
How long would each take to reach the Sun?
Assuming the object-Sun path was perpendicular to the ecliptic & the Sun had its actual motion, would the objects hit the Sun, or (roughly) by how much would they miss it?


texts: Is the rotation of the Sun and the rotation/orbit of the Moon around the Earth a coincidence?

texts:
While looking at sunspot information in connection with Amateur Radio, I found that the Sun rotates on a period from 27 days to 31 days.  Its rotation is differential, at the equator it spins at a rate of about 27 days, while at the poles it's closer to 31 days.

Earth's moon also rotates at a rate of 27.3 days.

I suspect this is nothing more than coincidence, but was wondering if there is more than a coincidental connection between these two rates of rotation, similar to how tidal locking forces the moon's rotation and orbit around earth to be the same rate.


texts: How to derive the equation for the age of a flat universe with a positive cosmological term?

texts: Can anyone show the steps involved in deriving this equation from the friedmann equation with the cosmological constant involved


texts: How did UV from the earliest stars 'alter the state of the 21 cm line' such that it shows up in CMB today?

texts:
In this question I discuss the recent (open access) paper in Nature An absorption profile centred at 78 megahertz in the sky-averaged spectrum at length. The abstract begins:

  After stars formed in the early Universe, their ultraviolet light is expected, eventually, to have penetrated the primordial hydrogen gas and altered the excitation state of its 21-centimetre hyperfine line. This alteration would cause the gas to absorb photons from the cosmic microwave background, producing a spectral distortion that should be observable today at radio frequencies of less than 200 megahertz(1).

where reference 1 is Jonathan Pritchard and Abraham Loeb (2012) 21 cm cosmology in the 21st century. From there I've found Leonid Chuzhoy and Zheng Zheng (2007) Radiative Transfer Effect on Ultraviolet Pumping of the 21 cm Line in the High-Redshift Universe.

I understand some basics about the hyperfine transition in hydrogen, and that the "spin temperature" of a gas in space can differ from the temperature of other partitions if it's being pumped, but these papers are more than a bit hard to read.

Is there a simple way to explain the basics behind how the exposure of hydrogen to the UV light produced in early stars would cause the "blip" in the (now red-shifted) 21 cm part of the Cosmic Microwave Background radiation spectrum we see today?


texts: What would our night sky look like if the solar system was 100 light years from the centre of the Milky Way

texts:
When we look at photo's of the centre of the Milky Way, it looks extremely bright due to the concentraion of star systems...

If our solar system was only 100 light years from the centre of the Galaxy, would we still have a dark night sky?


texts:
I understand that UT1 (and for that matter UT0, UT2, etc.) are based on averages of actual earth rotation, and serve as a form of mean solar time. However it’s not clear to me when these averages are taken and over what range? Certainly the average is taken over at least a year; but beyond that I can’t tell. Daily over the year? Yearly over the year; over several years?

How often and over what period is Earth’s rotation averaged to compute UT1?


texts: evaluate solar eclipse Besselian elements?

texts: I found this NASA website which says that to predict eclipse, we should solve the Besselian elements ..what does this mean, how can I solve for Besselian elements? Is there a numerical method? I need to find the circumstance (length of eclipse etc) at a given coordinate..Sorry I am  very new to astronomy so my question might be basic..